Conventionally, in orthodontics, before treating teeth of a patient, photographs of the teeth of the patient are taken and stored as data before treatment, and a plan for the treatment is made on the basis of those photographs. In addition, during the course of orthodontic treatment, a dentist or an assistant takes photographs of the interior of an oral cavity to store them as data for enabling both the dentist and the patient to know the progress of the treatment and for use as presentation materials in academic conferences. Intraoral camera is known to be useful in the art. Images of the oral cavity can be displayed for purposes of diagnosis, treatment, patient education and the like.
Generally, intraoral camera comprises illumination module, lens module and electrical parts. Illumination module is used to provide enough light to illuminate the teeth. Polarized illumination can remove the specular reflection. For old intraoral camera, halogen lamp and optical fiber are adopted to transfer the light. Now, intraoral camera using white LED becomes more and more popular due to plurality advantages such as small size, long lifetime and high luminous flux.
Intraoral camera should be capable of performing intraoral acquisition, arch acquisition, smile acquisition, and so on. In this regard, the lens module of the camera must have a big DOF and wide FOV in a large range of working distance that is from 1 mm to infinity. The camera will be used in a large working distance range and must keep a big DOF. Then focus adjustment is necessary to guarantee the good image quality.
For most of the intraoral camera, focus adjustment is performed by manually adjusting the distance between the lens and sensor. But this method is not convenient for dentists to operate. Some of the intraoral camera will use small NA that can provide big DOF to replace focus adjustment. But small NA optical system cannot provide high resolution and will increase the luminous flux.
While such systems may have achieved certain degrees of success in their particular applications, there is a need to provide an intraoral camera having auto focus adjustment.